Detailed plot summary - hunting and dividing
Hunting
The pig
Having failed to kill the pig earlier, Jack has something to prove and forms his hunters into an organised team. They go off on a hunt but this means the signal fire (which was also their responsibility) goes out and a passing ship fails to rescue them. Jack returns victorious with a dead pig but Ralph is furious. He thinks the most important things are survival and rescue. Jack believes that food is the first priority and that hunting is the way to get it.
An argument breaks out during which Piggy's glasses get broken. Despite their disagreements, the boys feast on the dead pig and Jack and the hunters act out the pig killing getting the boys overexcited.
The Beast
Ralph tries to restore order but the littluns' concern over the Beast is raised again. Several theories are put forward to explain who or what the Beast is. Simon, for instance, thinks that the Beast is really something evil inside themselves. Jack declares that whatever it is he will kill it, and wild dancing follows.
The parachutist
Meanwhile, in the skies above them, an unseen aerial battle takes place and a parachutist drifts down to the island landing near to the signal fire. An adult has finally appeared - but he is dead.
Dividing
The twins Sam and Eric are keeping the signal fire burning. When they see the parachutist's body they are convinced it must be the Beast and rush back to tell the others.
A further search the following day at first reveals nothing but late at night, Jack, Ralph and Roger all see the dead parachutist which confirms everyone's worst fears - there is a beast. After another argument with Ralph, Jack angrily leaves the group to be on his own. He goes on a pig hunt, kills one, and leaves its head on a stick as an offering to the Beast. It is soon swarming with flies.
Simon, who has also gone off on his own, comes across this bizarre sight - he hallucinates that the pig's head is talking to him and passes out. Simon calls the pig's head the Lord of the Flies.
Meanwhile, Piggy organises another signal fire to be built on the beach. Jack raids their camp to steal fire with which to roast his dead pig and invites the other boys to join his new group. Hungry, even Ralph and Piggy go along, but it is clear there are now two separate tribes.